On Dec. 28, 2013, it was announced by the German publication, Der Spiegel, the Cisco ASA/PIX firewall was one of at least 50 networking devices compromised by an NSA backdoor since at least 2008.[1] This assertion has since been evaluated by a Cisco PSIRT (Security Incident Response) team and refuted by Cisco [2]

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PIX was originally conceived in early 1994 by John Mayes of Redwood City, California and designed and coded by Brantley Coile of Athens, Georgia. The PIX name is derived from its creators' aim of creating the functional equivalent of an IP PBX to solve the then-emerging registered IP address shortage. At a time when NAT was just being investigated as a viable approach, they wanted to conceal a block or blocks of IP addresses behind a single or multiple registered IP addresses, much as PBXs do for internal phone extensions. When they began, RFC 1597 and RFC 1631 were being discussed, but the now-familiar RFC 1918 had not yet been submitted.

The design, and testing were carried out in 1994 by John Mayes, Brantley Coile and Johnson Wu of Network Translation, Inc., with Brantley Coile being the sole software developer. Beta testing of PIX serial number 000000 was completed and first customer acceptance was on December 21, 1994 at KLA Instruments in San Jose, California. The PIX quickly became one of the leading enterprise firewall products and was awarded the Data Communications Magazine "Hot Product of the Year" award in January 1995.[3]

After Cisco acquired Network Translation in November 1995, Mayes and Coile hired four longtime associates: Jim Jordan, Tom Bohannon, Richard Howes, and Pete Tenereillo (both who worked for NTI prior to the acquisition). Together they continued development on Finesse OS and the original version of the Cisco PIX Firewall, now known as the PIX "Classic". During this time, the PIX shared most of its code with another Cisco product, the LocalDirector.

On January 28, 2008, Cisco announced the end-of-sale and end-of-life dates for all Cisco PIX Security Appliances, software, accessories, and licenses. The last day for purchasing Cisco PIX Security Appliance platforms and bundles was July 28, 2008. The last day to purchase accessories and licenses was January 27, 2009. Cisco ended support for Cisco PIX Security Appliance customers on July 27, 2013.[4]

In May 2005, Cisco introduced the Adaptive Security Appliance (ASA) which combines functionality from the PIX, VPN 3000 series and IPS product lines. The ASA series of devices run PIX code 7.0 and later. Through PIX OS release 7.x the PIX and the ASA use the same software images. Beginning with PIX OS version 8.x, the operating system code diverges, with the ASA using a Linux kernel and PIX continuing to use the traditional Finesse/PIX OS combination.[5]

On Dec. 28, 2013, the German publication, Der Spiegel, revealed the Cisco ASA/PIX firewall was one of at least 50 networking devices compromised by an NSA backdoor since at least 2008.[6] Cisco subsequently opened a Security Response (PSIRT-1384943056)[7] on this issue and published a blog article by Cisco Senior Vice President, Chief Security Officer, John Stewart.[8]

The PIX runs a custom-written proprietary operating system originally called Finese (Fast Internet Service Executive), but as of 2014[update] the software is known simply as PIX OS. Though classified as a network-layer firewall with stateful inspection, technically the PIX would more precisely be called a Layer 4, or Transport Layer Firewall, as its access is not restricted to Network Layer routing, but socket-based connections (a port and an IP Address: port communications occur at Layer 4). By default it allows internal connections out (outbound traffic), and only allows inbound traffic that is a response to a valid request or is allowed by an Access Control List (ACL) or by a conduit. Administrators can configure the PIX to perform many functions including network address translation (NAT) and port address translation (PAT), as well as serving as a virtual private network (VPN) endpoint appliance.

The PIX became the first commercially available firewall product to introduce protocol specific filtering with the introduction of the "fixup" command. The PIX "fixup" capability allows the firewall to apply additional security policies to connections identified as using specific protocols. Protocols for which specific fixup behaviors were developed include DNS and SMTP. The DNS fixup originally implemented a very simple but effective security policy; it allowed just one DNS response from a DNS server on the Internet (known as outside interface) for each DNS request from a client on the protected (known as inside) interface. "Inspect" has superseded "fixup" in later versions of PIX OS.

The Cisco PIX was also one of the first commercially available security appliances to incorporate IPSec VPN gateway functionality.

PIX Device Manager (PDM) for PIX OS version 6.x, which runs over https and requires Java

Adaptive Security Device Manager (ASDM) for PIX OS version 7 and greater, which can run locally on a client or in reduced-functionality mode over HTTPS.

Examples of emulators include PEMU and Dynagen, and with NetworkSims.com ProfSIMs (Networksims) for a simulator.

Because Cisco acquired the PIX from Network Translation, the CLI originally did not align with the Cisco IOS syntax. Starting with version 7.0, the configuration became much more IOS-like. As the PIX only supports IP traffic (as opposed to IPX, DECNet, etc.), in most configuration commands "ip" is omitted. The configuration is upwards-compatible, but not downwards-compatible. When a 5.x or 6.x configuration is loaded on a 7.x platform, the configuration is automatically converted to 7.x formatting, as long as the configuration was using ACLs, versus conduits and "outbounds". This allows for an easy migration from PIX to ASA. PIX OS v7.0 is only supported on models 515, 515(E), 525 and 535. Although the 501 and 506E are relatively recent models, the flash memory size of only 8 MB prevents official upgrading to version 7.x, although 7.x can be installed on a 506E using monitor mode up to version 7.1(2). The 8 MB flash size only allows for installation of the PIX OS software, not the ASDM software (GUI). For the PIX 515(E) to run version >7.0, a doubling of the memory size is required (32->64 MB for restricted and 64->128 MB for Unrestricted/Failover licenses). A 515(E) UR/FO can run 7.0 with 64 MB memory installed, but that is not recommended as larger configuration and session/xlate tables can exceed the available memory.

The original NTI PIX and the PIX Classic had cases that were sourced from OEM provider Appro. All flash cards and the early encryption acceleration cards, the PIX-PL and PIX-PL2, were sourced from Productivity Enhancement Products (PEP).[13] Later models had cases from Cisco OEM manufacturers.

The PIX was constructed using Intel-based/Intel-compatible motherboards; the PIX 501 used an AMD 5x86 processor, and all other standalone models used Intel 80486 through Pentium III processors. Nearly all PIXs used EthernetNICs with Intel 82557, 82558, and 82559 network chipsets, but some older models are occasionally found with 3COM 3c590 and 3c595 Ethernet cards, Olicom-based Token-Ring cards, and Interphase-based FDDI cards.

Some Intel-based Ethernet cards for the PIX are identified at boot with the designation "mcwa" (Multi Cast Work Around). This designation denotes a multicast receive bug in the card's firmware.

Both the PIX 510 and 520 share basic components, such as motherboard, chassis, NICs, flash cards, etc., with the Cisco LocalDirector 416/420/430, the Service Selector Gateway 6510 (SSG-6510), and the Cisco Cache Engine CE2050, though the latter two run VxWorks, rather than a Finesse derivative.

The PIX boots off a proprietary ISAflash memorydaughtercard in the case of the NTI PIX, PIX Classic, 10000, 510, 520, and 535, and it boots off integrated flash memory in the case of the PIX 501, 506/506e, 515/515e, 525, and WS-SVC-FWM-1-K9.

The PIX technology implemented in the FWSM, for the Catalyst 6500 and the 7600 Router, has a part code of WS-SVC-FWM-1-K9.

The PIX535 has a PCI-X 66 MHz/64 bit bus for expansion slots. This results in a much higher cleartext throughput, as the PCI bus is no longer the bottleneck (the PCI bus is 33 MHz and 32 bits, resulting in maximum throughput of 1.2 GBit without overhead taken in account). As the lower Cisco ASA models use a PCI bus, the PIX535 was faster for cleartext than its successor ASA, until the introduction of the ASA5580.

???: 512 kB ISA flash card used in the original NTI PIX, PIX Classic and 10000. It is manufactured by Productivity Enhancement Products. Aside from progressive manufacturing refinements, the 512 KB and 2 MB flash cards were identical aside from the chips that populated it. Both booted from a 28F256 chip, but the 512 KB card only populated two of the flash sockets with 28F020 chips, while the 2 MB card populated all four sockets with 29C040 chips

???: 2 MB ISA flash card used in the PIX Classic, 10000, 510, and 520, as well as the SSG-6510 and many LocalDirectors. It is manufactured by Productivity Enhancement Products.

PIX-FLASH-16MB: 16 MB ISA flash card for the PIX 510, 520, and 535. It is manufactured by Productivity Enhancement Products.

Ethernet cards

PIX-1GE-66: 64 bit/66 MHz PCI 1000baseSX card for PIX 53x. Based on the Intel Pro/1000-F fiber network card using the Intel TL82543GC (Intel code name "Livengood") ASIC (PWLA8490sx[16]). The 1000baseT variant of this card, the Intel Pro/1000-t Server adapter (PWLA8490t[17]), is not supported by PIX OS, due to Carrier Extension[18] interoperability problems with early 1000baseT switch products[19]

PIX-1GE: 32 bit/33 MHz PCI 1000baseSX card for PIX 52x. Based on the Intel PWLA8490 Pro/1000 fiber network card with the 82542 (Intel code name "Wiseman") chipset. The ASIC used on this card is the LSI L2A1157/695314-003.[20] There is no 1000baseT variant of this card. In the release notes for PIX OS 6.02, Cisco advises against installing this card in the 525 and 535,[21] referencing caveat CSCdu00850, although this caveat actually only lists the PIX 535, which is the only model with a 66 MHz PCI bus.[22]

PIX-1FE: 32 bit/33 MHz PCI Single-port 10/100 Fast Ethernet card. Based on the Intel Pro/100+ family with the 82557, 82558 and 82559 chipsets.

???: 3COM 3c590 and 3c595 PCI NICs occasionally found in NTI PIX, PIX Classic, 10000, 510, 515, and 520. Mentioned in version 4.4.1 install guide and supported through at least PIX OS 5.1.5.[23] Since these are off-the-shelf PC components predating the creation of the PIX, there may not be PIX-specific part numbers for these at all.

^ Only the first few NTI PIXs came with the 486 processor; the rest came with a Pentium processor.^ The "inside" port is connected to an internal, unmanaged, auto-polarity 4 port switch.^ Restricted package / Unrestricted package limits (referred to by Cisco as R and UR/FO/FO-AA, respectively). For PIX-525, RAM configurations above 384 MB are not supported by Cisco however up to 3x 256 MB work for a maximum of 768 MB.^ According to Cisco, the 1000baseSX card is not officially supported by the 515/515e, but it will work.^ VAC acceleration vs VAC+ (in parenthesis) acceleration (Implies Unrestricted package).^ Older 520s made before February 2000 and with a serial number less than 18025677 shipped with a 2 MB flash card. Newer 520s shipped with a 16 MB flash card [80].^ The WS-SVC-FWM-1-K9 blade has no fixed ports or internal expansion; it makes use of either VLAN interfaces (being used by physical interfaces on a remote switch) or the physical interfaces on the switch/router it is installed in.^ PIX Classic firewalls with a serial number of 06002015 or lower came with a 512 KB flash card. Newer models came with a 2 MB flash card [81].^ The WS-SVC-FWM-1-K9 blade only supports IPSec VPN for management. It doesn't have the ability to terminate a VPN connection for remote users.^ The PIX 520 received updated PII processors as they became available, starting with the PII 233 and ending with the PII 350. The Intel-manufactured SE440BX-2ATX motherboard in the 520 can support any Slot1 processor from the Celeron Covington, Celeron Mendocino, Pentium II Klamath, Pentium II Deschutes, and the Pentium III Katmai families, as long as the cpu uses 2.0 V core voltage and can run on a 66 or 100 MHz fsb. One may also use 133 MHz FSB CPUs, but they will run at lower speeds, for example a 933 MHz CPU for 133 MHz FSB will only run at 700 MHz. A slotket can also be used to install the newer 500 MHz - 1.1 GHz Socket 370 Pentium III Coppermine cpus, as long as the slotket provides a voltage regulator and manual bus speed selector. Using the PowerLeap PL-iP3 converter, Tualatin processors can be used. A BIOS upgrade to the latest level of the SE440-BX2 is required. Using the bus-speed settings on the Powerleap, speeds of 1.6 GHz are possible.
The PIX 520 rev A firewalls may use the Intel AL440LX motherboard instead of the SE440BX-2. The AL440LX may be replaced by a SE440BX-2 motherboard, which is found in the 520 rev B.[24]^ Cannot be easily upgraded, due to clearance issues with the top cover.^ In early 2005, Cisco indicated that PIX OS 7.x would only support the 515, 515e, 525, and 535, while a "stripped-down" version would eventually be released for the 501 and 506e. While not officially supported, it is actually possible to update the 506E to 7.x code by removing all GUI management software.^ The maximum OS version one can run with a 512 KB card is 4.2(2). The maximum OS version one can run with a 2 MB card is 5.1(x). The maximum OS version with a 16 MB card is 6.3(5), unless one is using a PIX 535. OS version 5.2(4) and higher explicitly does not support the Intel 440FX chipset.^ Shows flash chips on the 2 MB flash card versus the chips on the 16 MB flash card.^ Various models of the 525 use different flash chips, probably due to differing production runs.^ Shows flash chips on the 512 KB flash card versus the chips on the 2 MB flash card.^ While the PIX 535 boots off of the same ISA flash card as some PIX 510s and 520s (the PIX-FLASH-16MB) its newer on-board PIX BIOS (version 4.x) overrides the PIX BIOS on the flash card (version 3.6) at boot.^ Since both the 510 and 520 have standard ATX motherboards, the PCI slot count can be higher or lower than the default if the motherboard is replaced with a different one.^ The performance figures cited here are highly changeable, as one can upgrade the CPU in the PIX 520 to a 1 GHz Pentium III, which will considerably increase its throughput in all of the below categories, putting it on a level with the 525 and 535.^ According to a 2000 field notice, due to a "procedural error", PIX 525s with serial numbers 44480380055 through 44480480044 were manufactured with erroneous or omitted EEPROM programming in their 82559 chips that caused the onboard FastEthernet ports to behave erratically when set to full-duplex. Starting with PIX OS 5.3.1, the "eeprom update" command will reprogram the defective data and restore normal operation permanently. Viewing the field notice requires registration [82]. Most, if not all, 525s in use today within that range have likely been corrected, but an unused or unopened unit within that range would still need the corrective action to be taken.^ It is theoretically possible to upgrade the Socket 8Pentium Pro processor in the PIX Classic and 10000 with either an Intel Pentium II Overdrive (300 or 333 MHz depending on the system bus speed)[83] or a Powerleap PL-Pro/II Celeron adapter [84], both of which are long out of production. The Powerleap adapter natively can allow use of a 300 - 533 MHz Mendocino Celeron PPGA processor. Coupled with the Powerleap Neo S370 FC-to-PPG adapter, one can use a 533 - 766 MHz FC-PGA Coppermine-128 Celeron processor. However, the 60 or 66 MHz bus (no 100 MHz bus) and 72-pin SIMM memory limitations of the workstation-style 440FX board used limit the potential gains in performance to be had from such upgrades. Upgrading the motherboard to a compatible server-style 440FX board with DIMM slots may allow for the use of the 440FX chipset's theoretical limit of 1 GB of RAM, although if the motherboard is to be replaced, it may arguably be more cost-efficient to upgrade to a SE440BX-2 motherboard with a slocket and Tualatin Celeron CPU. It is also worthwhile to note that PIX OS later than 5.3.4 explicitly does not support the 440FX chipset.^ The PIX 525 is known to come with a variety of processors including 1.65 V 600 MHz (SL3VH) and 1.75 V 600 MHz (SL5BT). It would appear that all 1.65 V to 1.75 V 100 MHz FSB CPUs would work, this has been substantiated to 1000 MHz with a SL5QV 1.75 V CPU.^ The first PIX Classics did not support failover. Only after this feature debuted with the LocalDirector did it come to be included in the later PIX Classics.[25]

PIX 506E overclocked specs

^ Proof of successful overclocking of Cisco Pix 506E with mainboard, socket and circuits modification for 1.2 GHz P3(Tualatin core) is on the photos. This mod was done by someone called i8.

^ The PIX 515E can be upgraded with the Coppermine P-III SL5QV 1Ghz processor. Due to heat concerns, it is advisable to remove the original heat sink heat transfer "sticker" and replace with good quality processor heat sink thermal compound.

^Deal, Richard (2009). Cisco ASA Configuration. Networking Professional's Library. McGraw Hill Professional. p. 263. ISBN9780071622684. Retrieved 2014-05-07. The timeout dcd parameter specifies that when a TCP session times out from the set connection timeout tcp command, the appliance should send a Dead Connection Detection (DCD) probe on the connection to both devices associated with the connection [...]. If one of the end devices doesn't respond [...] the appliance removes the connection.